Information Notice 1988-56, Potential Problems with Silicone Foam Fire Barrier Penetration Seals

Potential Problems with Silicone Foam Fire Barrier Penetration Seals

ML031150042
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	08/04/1988
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-88-056, NUDOCS 8807290111
Download: ML031150042 (9)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 August 4, 1988 NRC INFORMATION NOTICE NO. 88-56: POTENTIAL PROBLEMS WITH SILICONE FOAM

FIRE BARRIER PENETRATION SEALS

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice is being provided to alert addressees to potential

problems in their installed fire barrier penetration seals that could result

in the reduction of fire-resistive capabilities for protection of safety-related

redundant equipment and electrical power and control circuits. It is expected

that recipients will review this information for applicability to their facili- ties and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice do not constitute NRC require- ments; therefore, no specific action or written response is required.

Description of Circumstances

.

In May 1987, B&B Promatec submitted a 10 CFR Part 21 notification advising NRC

that some silicone foam fire barrier penetration seals at Wolf Creek Nuclear

Generating Station (WCNGS) did not meet minimum requirements. The noncon- forming conditions reported by B&B Promatec were described as voids, shrinkage, and lack of fill. The conditions were not obviously visible because they were

masked by fire-resistant boards that were typically installed on both sides of

a wall penetration and the bottom side of a floor penetration. WCNGS licensee

personnel found the problems during replacement of damaged fire-resistant boards.

Thereafter, WCNGS adopted an inspection methodology in which the fire boards

were removed, the silicone foam barriers were inspected and reworked as neces- sary, and the boards replaced.

Initial results from sample inspections indicated that over 25 percent of the

inspected seals were nonconforming. Additional inspections performed before

October 1987 revealed that 107 of 430 inspected seals required repair or rework

and that 65 of the 107 contained voids. The licensee for WCNGS subsequently

determined that the void problem was caused, at least in part, by underfill

at the time of installation. As a result of the WCNGS report, NRC has been

evaluating whether the silicone foam nonconforming conditions found at WCNGS

have generic applicability for plants other than those notified by B&B Promatec.

Part of this evaluation included a review of abstracts of licensee event reports.

880729011 Z-D

IN 88-56 August 4, 1988 Information obtained from this review indicates that a number of licensees

reported various fire barrier penetration seal nonconforming conditions. have

of the previously reported nonconforming conditions appear to be similar to Some

reported for WCNGS but are not limited to any particular vendor or installer.those

Silicone foam was the only fire barrier penetration seal material that was

specifically mentioned in the information reviewed, although some reports

not specifically identify the particular sealing material for the affected did

seals.

On the basis of this information, NRC believes that if generic problems exist, they may be limited to only silicone foam fire barrier penetration seals

not to any particular vendor or installer. but

Discussion:

This notice alerts addressees of the possibility that some installed fire

penetration seals may contain nonconforming conditions such as splits, gaps,barrier

voids, and lack of fill in the sealing material. These conditions may not

detected during routine inspection because the surface of the seal material be

typically covered by a fire-resistant dam material. Information that Is is

able suggests that the extent of the possible problem may be limited to fireavail- barrier penetrations filled with silicone foam material.

Silicone foam has been used extensively as a fire barrier penetration sealing

material in many nuclear power plants since the early 1970's. For silicone

foam seals installed since the mid 1970's, the silicone sealing material

been formulated of a two-component RTV 3-6548 base product manufactured has

by

Corning. The silicone foam seals are produced by mixing the two components,Dow

which then chemically react ("snap") a short time after they are mixed.

resulting snap causes gas formation and material expansion, which producesThe

silicone foam cell structure. Experience with silicone foam indicates that a

any one of many factors could affect the adequacy of the final seal instal- lation. These factors include the method of installation (e.g., damming

technique), technical and quality control of material, material mixing process, pouring and curing process, method of final inspection, training and experience

of installing personnel, and environmental factors, such as temperature and

humidity. Loss of control for any one of these factors could result in

that do not meet minimum requirements. seals

In many silicone foam fire barrier penetration seals, a permanent dam constructed

from a fire-resistant material is used. These dams must be present if they

part of the qualified seal design. Normally, a permanent dam is located were

on the

bottom of floor and ceiling penetrations and on both sides (although sometimes

only on one side) of wall penetrations. One common installation method used

the past called for installing the permanent damming material first so that in

would contain the liquid seal material during pouring and curing. Since it

the

permanent dam was part of final installation and because removal and reinstal- lation of the dam could be difficult and time consuming, final inspection

of

many silicone foam seals was performed with the permanent dam in place.

this approach was used, final determination of whether a proper seal had When

attained was made without direct visualinspection of the seal surface, been

which

appears to be a questionable practice. Instead, indirect methods of checking,

IN 88-56 August 4, 1988 such as tapping on the dam or inserting probe wires through the dam, were used.

In addition to precluding direct visual inspection of a new seal, installed dams

also hinder subsequent detection of nonconforming conditions that may have been

present since initial installation or that may have developed after initial

installation.

As mentioned earlier, licensees have reported various fire barrier penetration

seal nonconforming conditions in the past. The reported conditions that suggest

a generic problem are discussed below:

Voids - One nonconforming condition for silicone foam seals is the presence of

voids. Voids can be created in a number of ways. First, proper preparation of

the volume to be sealed is required before liquid fill. Proper preparation

includes ensuring that the penetrating items (pipes and cables) have sufficient

separation to permit the liquid to fill all the space in the volume. Second, the mixed sealing material requires a sufficiently long "snap" time to ensure

that the expansion process does not prevent free flow of sealing liquid to all

spaces in the volume. Third, the gas formed during the expansion process needs

to diffuse from the material without creating large gas bubbles or pockets.

Finally, a sufficient quantity of sealing material must be injected to ensure

that all spaces within the volume will be filled.

Gaps - Another nonconforming condition is the presence of gaps or the pulling

away of silicone foam material from the surface of penetrating items or inside

surfaces of the fire barrier. In some cases, these gaps extend only a short

distance into the seal thickness. In a few cases, gaps have been observed to

extend completely through the entire thickness of the seal. Causes of the gaps

have been variously given as failure to inject sufficient sealing material

during filling, bulging of damming material, shrinkage of silicone foam, and

contraction of silicone foam caused by a temperature change. The physical

characteristics of the silicone foam are such that a 1 percent reduction in

volume can be expected for a decrease of 200 F in temperature.

Splits - A third nonconforming condition is splitting (cracking of solidified

material) of the silicone foam material. This condition was not reported at

WCNGS but was reported by other licensees. In conversations with NRC, B&B

Promatec stated that the reasons for silicone foam splitting are not completely

understood and that splitting is a topic of discussion in the power sealer and

insulation industry.

Some of the actions taken by licensees as a result of finding nonconforming

silicone foam fire barrier penetration seals include (1) programs for inspec- tion and periodic reinspection of installed seals, (2) repair of nonconforming

seals, (3) evaluation of alternative materials for repairing old seals and in- stalling new seals, and (4) development of alternative methods for installing

and inspecting new silicone foam seals.

IN 88-56 August 4, 1988 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the technical

contacts listed below or the Regional Administrator of the appropriate regional

office.

es.osslDr

Division of Operat nts Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Joseph J. Petrosino, NRR

(301) 492-0979 C. Vernon Hodge, NRR

(301) 492-1169 Attachment: List of Recently Issued NRC Information Notices

Attachment

IN 88-56 August 4, 1988 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. - Subject Issuance Issued to

88-55 Potential Problems Caused 8/3/88 All holders of OLs

by Single Failure of an or CPs for nuclear

Engineered Safety Feature power reactors.

Swing Bus

88-54 Failure of Circuit Breaker 7/28/88 All holders of OLs

Following Installation of or CPs for nuclear

Amptector Direct Trip power reactors.

Attachment

88-53 Licensee Violations of NRC 7/28/88 All manufacturers and

Regulations, Which Led to distributors of radio- Medical Diagnostic pharmaceuticals for

Misadministratfons human use, nuclear

pharmacies, and

medical licensees.

88-52 Failure of Intrauterine 7/27/88 Medical licensees.

Tandem of Fletcher

Applicator Brachytherapy

Devices During Patient

Treatment

88-46, Licensee Report of 7/26/88 All holders of OLs

Supplement 1 Defective Refurbished or CPs for nuclear

Circuit Breakers power reactors.

88-51 Failures of Main Steam 7/21/88 All holders of OLs

Isolation Valves or CPs for nuclear

power reactors.

88-50 Effect of Circuit 7/18/88 All holders of OLs

Breaker Capacitance or CPs for nuclear

on Availability of power reactors.

Emergency Power

OL = Operating License

CP = Construction Permit

IN 88-56 August 4, 1988 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact one of the technical

contacts listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Joseph J. Petrosino, NRR

(301) 492-0979 C. Vernon Hodge, NRR

(301) 492-1169 Attachment: List of Recently Issued NRC Information Notices

Transmitted from DRIS on June 22, 1988

• SEE PREVIOUS CONCURRENCES

• SEE PREVIOUS PAGE FOR CONCURRENCE

• OGCB:DOEA:NRR *RPB:ARM *C/OGCB:DOEA:NRR *D:DRIS:NRR

CVHodge TechEd CHBerlinger BKGrimes

07/22/88 07/19/88 07/26/88 07/28/88

• D:DEST:NRR 4 RR

LShao CERos/

07/29/88 07ttj /88 i

IN 88-XX

August xx, 1988 No specific action or written response is required by this Information notice.

If you have any questions about this matter, please contact the technical

contact listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Joseph J. Petrosino, NRR

(301) 492-0979 Attachment: List of Recently Issued NRC Information Notices

Transmitted from DRIS on June 22, 1988

• SEE PREVIOUS CONCURRENCES

• SEE PREVIOUS PAGE FOR CONCURRENCE

• OGCB:DOEA:NRR *RPB: ARM *C/OGCB:DOEA:NRR *D:DRIS:NRR

CVHodge TechEd CHBerlinger BKGrimes

07/22/88 07/19/88 07/26/88 07/28/88 D:DP D:DOEA:NRR

LSh "o:' CERossi

07/ /88 07/ /88

IN 88-XX

July xx, 1988 No specific action or written response is required by this information notice.

If you have any questions about this matter, please contact the technical

contact listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Joseph J. Petrosino, NRR

(301) 492-0979 Attachments:

1. Partial List of Reports of Nonconforming Condit ions in

Fire Barrier Penetration Seals

2. List of Recently Issued NRC Information Notices

Transmitted from DRIS on June 22, 1988

• SEE PREVIOUS CONCURRENCES

OGCB:DOEA:NRR *RPB:ARM C/OGCB:DO A:NRR D:DOEA:NRR

CVHodge TechEd CHBerlinger CERossi

07/7,,V88 07/19/88 07/6&88 07/ /88 P/reB:SK

D40M .tIRz.

nme.

~*e

7bsltB%&^

I,.88-04, Supplement 1 July xx, 1988 No specific action or written response is required by tUs information notice.

If you have any questions about this matter, please cotacV the technical

contact listed below or the fegional _idministrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Joseph J. Petrosino, NRR

(301) 492-0979

9A;

Attachments /' 4e X

i¢- 7

1. Partial ary-of NonconformingAPenetration Seals

2. List of Recently Issued NRC Information Notices

<7.

Aej {DE

fe J0 5 D/DOEA:NRR

CERossi

07/ /88 OGCB:DOEA:NRR RVIB:DRIS:NRR ECEB:DEST:NRR (PB:ARM C/OGCB: DOEA:NRR

CVHodge JJPetrosino DKubicki TechEd CHBerlinger

07/ /88 07/ /88 07/ /88 07///i/88 07/ /88